1. Field of the Invention
The present invention generally relates to inferring the sources of interference among multiple emitter and receiver platforms (e.g., multiple radar systems) in which certain parameters of the emitters and receivers are known a priori (e.g., deduced or presumed).
2. Description of the Related Art
Generally, a radar unit will include an emitter which transmits a signal having a specific frequency. The signal is reflected from objects (e.g., backscattering) to a receiver of the radar unit. The radar units also include a signal processing pathway which processes only the frequency transmitted by the emitter.
However, a problem arises with conventional systems. When two or more radar systems are physically close to one other and are operating at the same frequency, they may interfere with one other. For example, a mobile unit, such as a ship, may have several radars which could, because of their proximity, create difficulties in properly determining the nature of signals which they receive. Such phenomena often arise when two emitters from two different radar devices transmit signals of the same or similar frequency. In such a situation, each signal processing pathway might receive the signal transmitted by the other radar unit and misinterpret the received signal as backscattering. Similarly, each of the signal processing pathways could receive a combination of direct signal transmission from an adjacent emitter and backscattering, which may or may not be in phase with each other, resulting in an incorrect or unclear reception pattern.
In order to overcome such problems, conventional radar units can be combined into a larger radar system. Such a radar system would control each of the individual radar units to avoid having closely spaced radar units operating at the same frequency. For example, such a system would receive information regarding the position of all radar units within the given radar system and, if two radar units were within a predetermined distance from one another, the system would change the operating frequency of one or both radar units.
While such a conventional radar system avoids direct interference, there is still interference among radar units which are not as closely spaced and among radar units which are operating at different, but relatively close, frequencies.
Also, there may be enemy traffic in the vicinity attempting to defeat transmission of information by purposely introducing noise into the signals of interest. Such jamming effects are especially troublesome, and statistical methods are needed to ascertain the sources of such intentional noise in addition to the sources unintentionally introducing spurious information.